Integrated circuits typically originate from semiconductor wafers. The production of semiconductor wafers is based on a number of different operations, including masking, etching, deposition, planarization, etc. Typically, planarization operations are based on a chemical mechanical planarization (CMP) process. During CMP processes, a wafer carrier holds and rotates the semiconductor wafer while the wafer contacts a CMP pad. In particular, during the planarization process, the CMP system applies pressure to the wafer carrier causing the wafer to press against a polishing surface of the CMP pad. The wafer carrier and/or the polishing surface of the CMP pad are rotated relative to each other to planarize the surface of the wafer.
Another method for planarizing wafers includes electrochemical-mechanical planarization (ECMP), in which electric potentials are applied to the wafer while it undergoes a CMP process. In a conventional ECMP system an electric potential is applied to the wafer with an electrolytic planarizing liquid. The electric potential applied to the wafer causes metal ions to be driven from the metal layer of the wafer via electropolishing, while additional material is removed via electrochemical-mechanical polishing. Accordingly, the over removal rate is characterized by the following equation:Removal rate=electropolishing (EP) rate+electrochemical-mechanical polishing (ECMP) rate,  (1)where the EP rate is the rate at which material is removed solely by electrical polishing, and the ECMP rate is the rate at which material is removed by the chemical solution in combination with both the physical application of the pad to the surface of the wafer and additional electrical interactions. However, the uncontrolled application of both electropolishing and ECMP to the wafer may not produce an overall material removal rate that is acceptably uniform.